Tubular food casings, particularly sausage casings, are supplied to sausage manufacturers in strands, particularly shirred strands, open at both ends. In order to manufacture a sausage product, individual shirred strands of casing are placed on stuffing horns and filled with the sausage emulsion. Prior to commencement of the said filling, it is necessary for an operator to manually de-shirr a short length of casing from the end of the shirred strand to effect a closure, or alternatively to hold it closed until sufficient sausage emulsion has been extruded into the end of the casing so as to prevent the flow of the sausage emulsion out of the casing. This manually performed operation considerably slows the sausage manufacturing procedure.
Automated machines have now been developed for the stuffing and/or stuffing and linking of shirred sausage casings and the use of these machines, as for example that disclosed in the U.K. Pat. No. 1,563,571, can greatly increase the rate of sausage production. With the advent of high speed automatic sausage stuffing machines, there is a need for a shirred casing strand having a closed end so that the shirred casing strand can be placed, manually or automatically, on a stuffing horn and filled with sausage emulsion without further action on the part of the machine operator.
Recent attempts have been made to close the ends of strands of casing by various techniques, twisting as shown in U.K. Pat. No. 1,082,222 and U.S. Pat. Nos. 4,070,729 and 4,075,938, compressed plugs as shown in U.S. Pat. No. 3,892,869 and U.K. Pat. No. 1,080,387, the use of adhesives as shown in U.K. Pat. No. 1,426,355 as well as knotting and heat sealing the casing material.
However, it has been found that when the shirred casing is of thin-wall construction, e.g., edible collagen casing of wall thickness 0.0007" to 0.001", a number of problems occur.
In some cases the closure that is formed has insufficient strength to prevent blowout of the end under pressure of the sausage emulsion. In other cases the closure formed allows a double thickness of casing material to be trapped between the stuffing horn and the control chuck or breaking ring during loading of the shirred strand. This usually results in casing rupture as it is subjected to the pressure of the sausage emulsion. Thirdly, the end seal may be of such integrity that there is no possibility that the pressure of the incoming sausage meat on the entrapped air be dissipated. This equally results in casing rupture.